Problem compiling for ruby 1.9.2-p180

I am trying to build MRI 1.9.2-p180. As far as I can tell, everything succeeds without error. However, when I try to load rubygems I get a LoadError for (which is required in the thread.rb file). See the gist below for all details. I can confirm that the library is not being built but I don't know why.

The source is from github and corresponds to commit id (b593b831d3caee7620ce028a0171cc0c7280d861). That is the commit tagged as the release on branch ruby_1_9_2.

Here is a complete log of the configure and make operations. You can see the commands I pass on the command line within the output as well.

In the 'make clean' operation I see that the directory ruby/ext/thread is cleaned. Later in the compilation process as the makefile steps through building things in each of the ruby/ext/* dirs, I never see it try to build anything in ruby/ext/thread. That explains why the library is missing but I don't know why the makefile is skipping that library.

The environment is Ubuntu on the Amazon EC2 cloud. The output of 'uname -a' is included in the gist.

Lastly, the tmpinstalldir/bin directory is on the PATH. I tried setting RUBYLIB to ~/repositories/ruby/lib/1.9.1/x86_64-linux but since is missing anyway that is of no help at all.

Anyone have an idea? If you need more information, please ask.